Though tessellation is determined on a per-object basis, you can manage how Maya handles the tessellation settings for the scene.
By default, Maya optimizes the tessellation settings for surfaces by:
For more information on tessellation, see Introduction to Tessellation and Approximation.
You can turn these optimization settings on or off in the Memory and Performance Options section of the Render Settings window.
Though raytracing quality is set by the options in the Raytracing Quality section of the Render Settings window (see Set raytracing quality), you can set scene optimization options in the Memory and Performance Options section of the Render Settings window.
For more information on raytracing, see Raytraced shadows in the Lighting guide.
You can control the number of processors for interactive rendering. To render with multiple processors, see Network render with Maya software.